Craniofacial hard tissue structures of middle and primary school students from Naqu, Tibet: X-ray cephalometric measures of 200 cases

Yue ZHAO; Keqiang HUANG; Chunshan LI

ABSTRACT

BACKGROUND:

Craniofacial hard tissue structures vary in age, gender, regional and racial differences. Some researchers have conducted X-ray cephalometric measures of malocclusion deformity in some domestic cities, and obtained normal cephalometric measures of craniofacial hard tissue structure. However, little data have been available concerning cephalometric measures of craniofacial hard tissue structure of Tibetan youth in Tibet region.

OBJECTIVE:

To observe structural features of craniofacial hard tissue of permanent tooth occlusal period in the adolescent of Lhasa. DESIGN, TIME AND

SETTING:

Stratified cluster sampling survey was performed at Naqu, Tibet from June to August 2008.

PARTICIPANTS:

A total of 200 adolescents at permanent tooth occlusal period, 100 males and 100 females aged 11-14 years were selected from middle and primary schools of Lhasa in 2003. The inclusion criteria included teeth in order, neutral occlusal adjustment, normal maxilla and mandible appearance and relationship, normal teeth number and overbite and overjet, concordant face, and no history of orthodontic management.

METHODS:

According to the requirements and standards for the irradiation, 200 subjects underwent X-ray cephalometric measures, and the results were compared with normal values of the same age. MAIN OUTCOME

MEASURES:

SNA angle, SNB angle, ANB angle, 1-SA angle, 1-NA angle, 1-NA, T-MP angle, Y axial angle, NP-FH angle, NA-PA angle, 1-T angle, MP-SN angle, Po-NB, T-NB angle, T-NB, and MP-FH angle.

RESULTS:

No significant differences were found between Lhasa adolescents and normal values in terms of SNA angle, SNB angle, ANB angle, 1-SN angle, 1-NA angle, 1-NA, T-MP angle, Y axial angle, NP-FH, NA-PA, 1-T, and MP-SN. Po-NB was slightly greater than normal value and T-NB angle, T-NB and MP-FH were significantly less than normal values.

CONCLUSION:

Lhasa adolescents have significantly different craniofacial hard tissue structure from normal values forward protrusion of mental region, flat mandible angle, straight mandible anterior teeth, upward and forward rotated mandible, and straight face type.